Method and apparatus for plating threaded portion of high pressure gas cylinder

ABSTRACT

A method and apparatus for plating a threaded portion of a high pressure gas cylinder is provided. The method includes: providing a high pressure gas cylinder having a gas containing portion and a threaded portion being formed on a top of the gas containing portion; locating an anode pipe, in which a plating solution passage is formed, inside the threaded portion; forming a closed chamber containing the threaded portion and the anode pipe; forming a flux of the plating solution inside the closed chamber; and forming a voltage difference between the anode pipe and the threaded portion, and plating the threaded portion.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application Nos. 2006-0056795, filed on Jun. 21, 2006, and 2007-0037559 filed on Apr. 17, 2007 in the Korean Intellectual Property Office, the entire disclosure of both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for plating a threaded portion of a high pressure gas cylinder, and more particularly, to a method and apparatus for plating a threaded portion which can maintain a unique characteristic of a corrosive gas or high-purity gas.

2. Description of Related Art

Various types of industrial gases are used according to purposes in business fields such as biochemistry, precision machinery industry, medical science, semiconductor industry and the like. It is very important to take appropriate treatment on the inside of cylinders to maintain a unique characteristic of a corrosive gas or a high-purity gas in the case of a predetermined process using the corrosive gas or the high-purity gas. Otherwise, the industrial gases should be contaminated by foreign substances which exist on an inside wall of a high pressure gas cylinder after being charged into the high pressure gas cylinder, and a physical or chemical characteristic of the industrial gases may be changed due to a chemical reaction occurring between the inside steel wall of a gas cylinder and the charged gas. Accordingly, appropriate treatment is required to be taken with respect to the gases to maintain the unique characteristic.

To maintain the unique characteristic with respect to the industrial gases, a manufacturing method of a high pressure gas cylinder using a chemically stable material may be provided, and nickel is generally used for the chemically stable material. However, in the case of the above method, a manufacturing cost for the high pressure gas cylinder is high since a high-purity raw material is not easy to acquire. Also, in the case of the above method, a high pressure charge is comparatively difficult than a gas cylinder made of a steel, and costs for storage and transportation may be higher.

Also, a method for plating a metal on an inner surface of a gas cylinder made of steel may be provided, the metal being chemically stable with respect to the industrial gases. However, as described later, it is difficult to form a flawless plating layer on a threaded portion, the threaded portion being provided with a valve, of a high pressure gas cylinder with the above-described methods. Accordingly, an expected characteristic of a charged gas may be deteriorated since the raw material of the threaded portion may chemically react to a charged gas. For a conventional method for plating, the following two methods may be taken into consideration.

A first method is to form a plating layer thickly on an inside wall of the high pressure gas cylinder. In this case, the plating may be performed using a material which is chemically stable with respect to the industrial gas, and nickel is generally used for the material. A top of the high pressure gas cylinder is processed in a threaded form to couple with a valve. During the processing, the top of the high pressure gas cylinder is threaded and punctured via a mechanical process. Subsequently, a method capable of maintaining a plating layer by forming a sufficiently thick plating layer, after the machining process, may be provided. However, the thickness of the plating layer satisfying the above condition is beyond the scope that can be embodied in general electroplating.

A second method is to perform a first plating with respect to an inside wall of a high pressure gas cylinder, and to perform a second plating with respect to a threaded portion after a mechanical process of the threaded portion. However, this method has problems, and the problems are disclosed in U.S. Patent Publication No. 6089399 and 7032768. Due to the following problems, a method of inserting an additional threaded portion is used in the specification of the present invention.

When plating thickness is too thick, it is difficult to couple with the valve, and when plating thickness is too thin, a charged gas may be leaked via a gap between the threaded portion and the valve, and therefore, thickness for plating the threaded portion should be appropriately controlled, however, the conventional method may not control the thickness for plating the threaded portion.

FIG. 6 is a cross-sectional view illustrating a shape of a plating layer being formed on a threaded portion according to a conventional method for plating.

As illustrated in FIG. 6, due to a characteristics of electroplating, a plating layer 620 is thickly formed on ridges 612 of a threaded portion, in which a high current flows, and the plating layer 620 is thinly formed on pits 614 of the threaded portion, in which a low current flows, or an air pocket may be formed on the pits 614 of the threaded portion. Air pockets may cause a defect on the pits 614 of the threaded portion, such as a pit or a pin hole. Due to the defect on a threaded portion 610, a chemical reaction between a raw material of the high pressure gas cylinder and a charged gas may occur, consequently a quality of the charged gas may be deteriorated.

Also, the conventional method has a problem in that micro-sized foreign substances being generated during a manufacturing process are exposed toward a surface from the pits 614 of the threaded portion to react to the charged gas. The micro-sized foreign substances being generated during the manufacturing process of the high pressure gas cylinder are isolated on the pits 614 of the threaded portion, and are exposed toward the surface of the threaded portion 610 during a plating process, consequently the exposed micro-sized foreign substances react to the charged gas to cause the above described problems.

BRIEF SUMMARY

An aspect of the present invention provides a method and an apparatus for plating a threaded portion of a high pressure gas cylinder which can maintain a unique characteristic of a gas, with respect to a corrosive gas or a high-purity gas, by forming a flawless plating layer on the threaded portion.

Another aspect of the present invention also provides a method and an apparatus for plating a threaded portion of a high pressure gas cylinder that enables to maintain a unique characteristic of a charged gas since foreign substances being generated during a manufacturing process of the high pressure gas cylinder are not isolated on pits of the threaded portion.

Another aspect of the present invention also provides a method and an apparatus for plating a threaded portion of a high pressure gas cylinder that enables to appropriately control thickness distribution of a plating layer being formed on ridges and pits of the threaded portion.

According to an aspect of the present invention, there is provided a method for plating a threaded portion of a high pressure gas cylinder including: providing a high pressure gas cylinder having a gas containing portion and a threaded portion being formed on a top of the gas containing portion; locating an anode pipe, in which a plating solution passage is formed, inside the threaded portion; forming a closed chamber containing the threaded portion and the anode pipe; forming a flux of the plating solution inside the closed chamber; and forming a voltage difference between the anode pipe and the threaded portion, and plating the threaded portion.

The present invention may circulate a plating solution to forcefully flow in the chamber, and the threaded portion of the high pressure gas cylinder may be plated by the circulating plating solution. Accordingly, a defect on a plating layer may be prevented by preventing occurrence of an air pocket, and may prevent foreign substances from existing on the pits of the threading portion.

In the present invention, circulation of the plating solution may be performed using an anode pipe and the closed chamber, the anode pipe being formed the plating solution passage. As an example, the plating solution is provided via an inside passage of the hollow anode pipe, and the provided plating solution may be flowed into the closed chamber through the plating solution passage, the plating solution passage being formed on a side of the anode pipe. The flowed plating solution is discharged to the outside through an inlet/outlet for the plating solution so that flux of the plating solution is formed around the anode pipe. As another example, the plating solution is flowed into the closed chamber via the inlet/outlet for the plating solution, and the flowed plating solution is discharged to an outside through an opened hole of the anode pipe. Also, the anode pipe may be located inside the threaded portion and the plating solution passage may be formed in correspondence to a bottom of the threaded portion so that the plating solution smoothly flows around the threaded portion. During the circulation of the plating solution, the plating layer may be formed on the threaded portion of the high pressure gas cylinder. In this instance, a material, which is chemically stable with respect to the industrial gas, may be used to perform plating, and nickel is generally used for the plating.

In the present invention, in the forming of the closed chamber, a bottom sealing portion isolates a bottom of the threaded portion from the gas containing portion, and a top sealing portion, which is formed in correspondence to the bottom sealing portion, isolates a top of the threaded portion from an outside to form the closed chamber.

Also, a diameter of the anode pipe is controlled so as to control thickness of the plating layer, the plating layer being formed on ridges and pits of the threaded portion. The plating layer may be thickly formed on the ridges of the threaded portion since a high current flows through the ridges of the threaded portion, and the plating layer may be thinly formed on the pits of the threaded portion since a low current flows through the pits of the threaded portion, accordingly a portion of the plating layer may be incompletely formed. However, in the present invention, the above problem may be solved by suitably controlling the diameter of the anode pipe for plating types, the anode pipe performing as an anode.

Specifically, when the diameter of the anode pipe is comparatively greater, since a ratio of a distance from a surface of the anode pipe to the pits of the threaded portion to a distance from the surface of the anode pipe to the ridges of the threaded portion is comparatively greater, plating deviation between the high current portion and the low current portion is subsequently increased. Conversely, when the diameter of the anode pipe is comparatively less, since the ratio of the distance from the surface of the anode pipe to the pits of the threaded portion to the distance from the surface of the anode pipe to the ridges of the threaded portion is comparatively less, plating deviation between the high current portion and the low current portion is subsequently decreased. Accordingly, deviation between the ridges and the pits of the threaded portion may be controlled within a predetermined range by controlling the diameter of the anode, more particularly, thickness deviation between the ridges and pits of the threaded portion may be controlled within a necessary range by controlling the diameter of the anode pipe according to locations, when it is required. Also, entire thickness of the plating layer may be controlled by controlling a current amount, which is required to perform the plating.

The present invention may control thickness of the plating layer according to locations by partially masking the anode pipe. Specifically, an outer surface of the anode pipe may be partially masked by winding a predetermined tape on a portion of the outer surface of the anode pipe, and electric charges between the masked portion and the threaded portion may not smoothly flow. Accordingly, the plating layer of the threaded portion around the masked portion of the anode pipe may be formed to be thinner than an un-isolated portion of the anode pipe. Consequently, the thickness of the plating layer may be controlled according to locations of the threaded portion by isolating a necessary portion.

The present invention may be generally applicable to when performing a second electroplating with respect to the threaded portion after processing the threaded portion on a top of the high pressure gas cylinder, the high pressure gas cylinder having the plating layer formed on an inside wall thereof. The plating layer may be made of a metal, such as nickel, which is chemically stable with respect to a corrosive gas or a high-purity gas.

According to another aspect of the present invention, there is provided an apparatus for plating a threaded portion of a high pressure gas cylinder including: an anode pipe, on which a plating solution passage is formed; a bottom sealing portion being formed on a bottom of the anode pipe, and isolating a bottom of the threaded portion from the gas containing portion; a top sealing portion being formed in correspondence to the bottom sealing portion, and isolating a top of the threaded portion from an outside; and a plating solution supplier supplying a plating solution to the anode pipe and the closed chamber.

The present invention may allow the plating solution to forcefully flow within the chamber to circulate, and the threaded portion of the high pressure gas cylinder may be plated by the circulating plating solution. Accordingly, a defect on a plating layer may be prevented by preventing occurrence of an air pocket, and may prevent foreign substances from existing on pits of the threading portion. Also, in the present invention, a diameter of the anode pipe is controlled so as to control the thickness of the plating layer, the plating layer being formed on ridges and pits of the threaded portion. Also, the present invention may control the thickness of the plating layer according to each location of the threaded portion by partially masking the anode pipe.

The plating solution passage formed in the anode pipe may be located in correspondence to a bottom of the threaded portion, i.e. on a top of the bottom sealing portion, so that the plating solution smoothly flows around the threaded portion. Accordingly, the plating solution which will be flowed into the closed chamber via the plating solution passage or which will be discharged from the close chamber may smoothly flow from the bottom to the top of the threaded portion. A number of the plating solution passages may be determined by considering a size of an inside of the threaded portion.

Also, at least one inlet/outlet for the plating solution may be formed to discharge the plating solution being flowed into the closed chamber via the plating solution passage or to flow the plating solution into the closed chamber. The inlet/outlet for the plating solution may be formed on a side of the top sealing portion, and may be formed in a pipe shape to be provided by a side of the anode pipe. In this instance, the shape or the location of the inlet/outlet for the plating solution is not limited to the above-mentioned description.

The bottom sealing portion may isolate a bottom of the threaded portion from the gas containing portion so that the plating solution does not flow into the gas containing portion. For a better performance of the isolating, the bottom sealing portion may include a supporter and a rubber piece on a bottom of the anode pipe. The supporter may have a diameter less than an inside diameter of the threaded portion, and the rubber piece may be located on an upper portion of the supporter and have a diameter greater than the inside diameter of the threaded portion.

The present invention may be generally applicable to when performing a second electroplating with respect to the threaded portion after processing the threaded portion on a top portion of the high pressure gas cylinder, the high pressure gas cylinder having the plating layer formed on an inside wall thereof. The plating layer may be made of a metal, such as a nickel, which is chemically stable with respect to a corrosive gas or a high-purity gas.

Additional aspects, characteristics, and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects, characteristics, and advantages of the invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a cross-sectional view illustrating an apparatus for plating a threaded portion of a high pressure gas cylinder according to an exemplary embodiment of the present invention;

FIG. 2 is a cross-sectional view illustrating a threaded portion according to an exemplary embodiment of the present invention;

FIG. 3 is a flowchart illustrating a method for plating a threaded portion of a high pressure gas cylinder according to an exemplary embodiment of the present invention;

FIG. 4 is a cross-sectional view illustrating an apparatus for plating a threaded portion of a high pressure gas cylinder according to another exemplary embodiment of the present invention;

FIG. 5 is a cross-sectional view illustrating an apparatus for plating a threaded portion of a high pressure gas cylinder according to still another exemplary embodiment of the present invention; and

FIG. 6 is a cross-sectional view illustrating a shape of a plating layer being formed on a threaded portion according to a conventional method for plating.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. Exemplary embodiments are described below to explain the present invention by referring to the figures.

FIG. 1 is a cross-sectional view illustrating an apparatus for plating a threaded portion of a high pressure gas cylinder according to an exemplary embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a threaded portion according to an exemplary embodiment of the present invention.

As illustrated in FIG. 1, the apparatus for plating the threaded portion of the high pressure gas cylinder according to an exemplary embodiment of the present invention includes an anode pipe 110, a bottom sealing portion 120, a top sealing portion 130, and a plating solution supplier 140. The apparatus for plating the threaded portion of the high pressure gas cylinder is for plating a threaded portion 154 of a high pressure gas cylinder 150. The high pressure gas cylinder 150 includes a gas containing portion 152 and the threaded portion 154, and the tread portion 154 is generally formed on a top of the gas containing portion 152. In this instance, the gas containing portion 154 may indicate a space for charging a gas inside the high pressure gas cylinder.

The anode pipe 110 may perform as an anode during an electroplating process, and also perform as a type of a pipe, in which a plating solution flows, using an inner space 112. The plating solution passage 114 is formed on the anode pipe 110. The plating solution passage 114 may be formed in correspondence to a bottom of the threaded portion 154, i.e. on a top of the bottom sealing portion 120, so that the plating solution smoothly flows around the threaded portion. Since the plating solution passage 114 is formed as described above, the plating solution may smoothly flow from the bottom to a top of the threaded portion 154, the plating solution being flowed into a closed chamber 132 via the plating solution passage 114. A number of the plating solution passages 114 may be determined by considering a size of an inside of the threaded portion 154.

Also, the bottom sealing portion 120 may be formed on a bottom of the anode pipe 110. The bottom sealing portion 120 isolates a bottom of the threaded portion 154 from the gas containing portion 152. For a better performance for the isolating of, the bottom sealing portion 120 may include a supporter 122 and a rubber piece 124. The supporter 122 may have a diameter less than an inside diameter of the threaded portion 154, and the rubber piece 124 may be located on an upper portion of the supporter 122 and have a diameter greater than the inside diameter of the threaded portion 154.

Hereinafter, a process of forming the closed chamber 132 will be described.

After locating the supporter 122 beneath the threaded portion 154, the rubber piece is located on a top of the supporter 122 using a pair of tweezers. After the supporter 122 and the rubber piece 124 are located beneath the threaded portion 154, the anode pipe 110 is pulled up so that the rubber piece 124 is closely contacted beneath the threaded portion 154, and the top of anode pipe 110 is fixed to the top sealing portion 130 using a nut 136. Consequently, the closed chamber 132 containing the threaded portion 154 and the anode pipe 110 may be formed.

The plating solution being supplied from the plating solution supplier 140 may be provided to the closed chamber 132 via the inner space 112 of the anode pipe 110. The provided plating solution may be flowed from the plating solution passage 114 to the bottom of the threaded portion 154, and the plating solution may be discharged to an outside via the inlet/outlet 134 for the plating solution after flowing from the bottom to the top of the threaded portion 154. In the exemplary embodiment of the present invention, the inlet/outlet 134 for the plating solution being formed on a side of the top sealing portion 130 is described, however the shape and the location of the inlet/outlet 134 for the plating solution is not limited to the exemplary embodiment of the present invention. A number of the inlet/outlets 134 for the plating solution may be determined according to a flowing speed of the plating solution.

During circulation of the plating solution, a plating layer 160 may be formed on an inside wall of the threaded portion 154. The plating layer 160 may be exclusively formed on the inside wall of the threaded portion 154, i.e. on a top of the rubber piece 124, since the plating solution is not flowed into the gas containing portion 152 due to the rubber piece 124. Also, since the plating layer 160 is generally formed on the inside wall of the high pressure gas cylinder 150, as illustrated in FIG. 2, when plating the threaded portion 154 using the apparatus for plating the threaded portion of the high pressure gas cylinder according to an exemplary embodiment of the present invention, disconnection of the plating layer 160 may not occur. Accordingly, an entire inside wall of the high pressure gas cylinder may be protected by the plating layer 160.

The apparatus for plating the threaded portion of the high pressure gas cylinder according to an exemplary embodiment of the present invention may form a flux of the plating solution by forcefully providing an inside of the closed chamber 132 with the plating solution, and the plating layer 160 may be formed on the threaded portion 154 due to the flux of plating solution. An air pocket does not occur on pits of the threaded portion 154 due to the forceful providing of the flux of the plating solution. Accordingly, defects of the plating layer 160, such as a pit and a pin hole, do not occur on the pits of the threaded portion 154. According to the present invention, a quality of a charged gas may not deteriorate since a chemical reaction between a raw material of the high pressure gas cylinder and the charged gas does not occur on the threaded portion 154. Also, according to the present invention, a plated surface of the threaded portion 154 is formed without micro-sized foreign substances since the micro foreign substances are compulsively discharged due to the compulsive flux of plating solution.

FIG. 3 is a flowchart illustrating a method for plating a threaded portion of a high pressure gas cylinder according to an exemplary embodiment of the present invention.

Processes of manufacturing a high pressure gas cylinder are generally as follows: Initially, a body of the high pressure gas cylinder is manufactured, and an end of the body of the high pressure gas cylinder is opened. The body of the high pressure gas cylinder may be provided in types of a spun cylinder by hot spinning, a deep drawn and ironed (DDI) cylinder by deep drawing, a billet pierced cylinder by an Ehrhardt process, and the like according to a way of manufacturing a closed bottom of the body of the high pressure gas cylinder. After forming a bottom of the body of the high pressure gas cylinder, a process of plating an inside wall of the high pressure gas cylinder is performed. After forming the plating of the inside wall of the high pressure gas cylinder, an opened upper end portion is formed into an inlet of the high pressure gas cylinder through a hot spinning process. And a threaded portion is formed in a thread shape on the inlet of the high pressure gas cylinder to couple with a valve, the valve being used to charge and discharge a gas.

In operation S301, i.e. in the process of the providing of the high pressure gas cylinder, the high pressure gas cylinder including a gas containing portion and a threaded portion is provided. The gas containing portion may indicate a space for charging a gas inside the high pressure gas cylinder.

During the process of forming the threaded portion, a plating layer being formed on the inside wall of the threaded portion may be eliminated since the processed portion of the high pressure gas cylinder is cut due to a mechanical process. In this instance, in a micro gap occurring between the threaded portion and the valve even a metal, i.e. a raw material of the high pressure gas cylinder, may react to a charged corrosive gas or a high-purity gas being charged in the gas containing portion when the valve is coupled with the threaded portion. Accordingly, an additional process for the plating with respect to the threaded portion is required since an expected characteristic of the charged gas may be deteriorated. For the additional process for the plating with respect to the threaded portion, operation S302 locating an anode pipe inside the threaded portion, in which a plating passage formed, may be performed. The anode pipe may perform as an anode during the electroplating.

In operation S303, a closed chamber which contains the threaded portion and the anode pipe is formed to prepare for a space to forcefully circulate the plating solution. In operation S303, a bottom sealing portion formed on a bottom of the anode pipe isolates a bottom of the threaded portion from the gas containing portion. Also, in operation S303, a top sealing portion formed in correspondence to the bottom sealing portion isolates a top of the threaded portion from an outside.

For a better performance for the isolating, the bottom sealing portion may include a supporter and a rubber piece on a bottom of the anode pipe. The supporter may have a diameter less than an inside diameter of the threaded portion, and accordingly, may reach the gas containing portion by passing through the threaded portion. The rubber piece may be located on an upper portion of the supporter and have a diameter greater than the inside diameter of the threaded portion, accordingly may isolate the threaded portion from the gas containing portion since the rubber piece is closely contacted to a bottom of the threaded portion. The bottom sealing portion may include a balloon portion, the balloon portion being formed on the bottom of the anode pipe. Prior to blowing up, the balloon portion may pass through the threaded portion. After the balloon portion passes through the threaded portion, the threaded portion may be isolated from the gas containing portion by expanding the balloon portion, expanded by inserting a fluid. An inner pipe may be formed inside the anode pipe so as to insert the fluid into the balloon portion.

In operation S304, a flux of the plating solution may be provided using the anode pipe and the closed chamber, the anode pipe being formed a plating solution passage. Specifically, the plating solution may be provided via an internal passage of the hollow anode pipe, the provided plating solution may be flowed into the closed chamber via the plating solution passage, the plating solution passage being formed on a side of the anode pipe. The flowed plating solution may flow along the threaded portion, and be discharged to an outside via an inlet/outlet for the plating solution. Conversely, the plating solution may be flowed into the closed chamber via the inlet/outlet for the plating solution, and be discharged to an outside via an opened hole on a side of the anode pipe. Also, the anode pipe may be located inside the threaded portion so that the plating solution smoothly flows around the threaded portion, and the plating solution passage may be formed in correspondence to a bottom of the threaded portion.

In operation S305, plating is performed by forming a voltage difference between the anode pipe and the threaded portion. Operation S305 may be simultaneously performed with operation S304.

In operation S305, the plating layer may be formed with thickness of approximately 1 to 100 μm. The plating layer may be formed with thickness greater than approximately 1 μm, more particularly 20 μm, since a defect, such as an oxide layer, on the threaded portion has been eliminated due to a mechanical process. In this instance, the plating layer may be formed with thickness of less than approximately 100 μm. When the plating layer is formed with thickness of greater than approximately 100 μm, it may be difficult to couple a valve.

In operation S305, a nickel chloride solution may be utilized to embody the plating layer, from the nickel chloride solution, the nickel chloride solution having a nickel chloride concentration of approximately 50 to 500 g/L, a boric acid concentration of approximately 5 to 50 g/L, a pH in the range of approximately 0.5 to 6.5, a use temperature of approximately 20 to 95° C., and a use voltage of approximately 3 to 20 V. A nickel sulfate solution is utilized to embody the plating layer, from the plating solution, the nickel sulfate solution having a nickel sulfate concentration of 100 to 500 g/L, a boric acid concentration of approximately 5 to 50 g/L, a nickel chloride concentration of approximately 2 to 80 g/L, a pH in the range of approximately 1 to 6.5, a use temperature of approximately 20 to 95° C., and a use voltage of approximately 3 to 20V. A nickel sulfamate solution is utilized to embody the plating layer, from the plating solution, the nickel sulfamate solution having a nickel sulfamate concentration of 100 to 500 g/L, a boric acid concentration of approximately 5 to 50 g/L, a nickel chloride concentration of approximately 2 to 80 g/L, a pH in the range of approximately 1 to 6.5, a use temperature of approximately 20 to 95° C., and a use voltage of approximately 3 to 20 V. A nickel fluoborate solution is utilized to embody the plating layer, from the plating solutions, the nickel fluoborate solution having a nickel fluoborate concentration of 40 to 500 g/L, a boric acid concentration of approximately 5 to 50 g/L, a pH in the range of approximately 1 to 6.5, a use temperature of approximately 20 to 95° C., and a use voltage of approximately 3 to 20 V.

FIG. 4 is a cross-sectional view illustrating an apparatus for plating a threaded portion of a high pressure gas cylinder according to another exemplary embodiment of the present invention.

The apparatus for plating the threaded portion of the high pressure gas cylinder according to the exemplary embodiment of the present invention may include an anode pipe 410, a bottom sealing portion 420, a top sealing portion 430, and a plating solution supplier 440.

The top sealing portion 430 may be formed on a top of the threaded portion 454 to isolate a top of a threaded portion 454 from an outside. A closed chamber 432 where a plating solution flows may be formed by the bottom sealing portion 420 and the top sealing portion 430. The plating solution supplier 440, supplying the plating solution into the closed chamber 432, may include a tank storing the plating solution, a pump pushing the plating solution, and a pipe 442 connecting the tank to the closed chamber 432. In the present specification, the pipe 442 is connected to an opened hole of the top of the anode pipe 410, however a configuration of the pipe 442 is not limited to the above description.

The plating solution may be provide into the closed chamber 432 via an inside space 412 of the anode pipe 410. The provided plating solution may flow from a plating solution passage 414 to a bottom of the threaded portion 454, the flowed plating solution may flow from the bottom of the threaded portion to a top of the threaded portion 454, and may be discharged to an outside via an inlet/outlet 434 for the plating solution. In the exemplary embodiment of the present invention, the inlet/outlet 434 for the plating solution is formed on a side of the anode pipe 410, however the shape or the location of the inlet/outlet 434 for the plating solution is not limited to the above-described exemplary embodiment of the present invention. During circulation of the plating solution, the plating layer may be formed on inside wall of the threaded portion 454.

FIG. 5 is a cross-sectional view illustrating an apparatus for plating a threaded portion of a high pressure gas cylinder according to still another exemplary embodiment of the present invention.

Referring to FIG. 5, a bottom sealing portion may include a balloon portion 520 being formed on a bottom of a anode pipe 510, and an inner pipe 516 may be formed inside the anode pipe 510 to insert a fluid into the balloon portion 520.

Prior to expanding, the balloon portion 520 may pass through the threaded portion 510. After passing through a threaded portion 554, the threaded portion 554 may be isolated from a gas containing portion 552 by blowing up the balloon portion, expanded by inserting a fluid. The balloon portion 520 may be made of a material with excellent chemical-resistance, durability, elasticity, and flexibility. An inner pipe 516 may be additionally formed inside the anode pipe 510 so as to insert the fluid into the balloon portion 520.

A closed chamber 532 may be formed as follows: After locating the balloon portion 520 beneath the threaded portion 554, the balloon portion expands by inserting the fluid into the balloon portion 520 via the inner pipe 516. The anode pipe 510 is pulled up so that the balloon portion 520 is closely contacted beneath the threaded portion 554, and an opened hole of the top of the inner pipe 516 is isolated so that the expanded balloon portion 520 may be maintained. The top of anode pipe 510 is fixed to the top sealing portion 530 using a nut 536. Consequently, the closed chamber 532 containing the threaded portion 554 and the anode pipe 510 may be formed.

The anode pipe 510 may be formed to have a length less than a length of the inner pipe 516 so that the plating solution may be flowed into the bottom of the threaded portion 554 via the plating solution passage 514.

The plating solution may be provided to the closed chamber 532 via an inner space 512 of the anode pipe 510, and the provided plating solution may be discharged to an outside via an inlet/outlet 534 for the plating solution after passing through the plating solution passage 514. During circulation of the plating solution, a plating layer may be formed on an inside wall of the threaded portion 554.

According to the above-described exemplary embodiments of the present invention, it is possible to provide a high pressure gas cylinder which can maintain a unique characteristic of a corrosive gas or a high-purity gas by forming a flawless plating layer with respect to an entire inside wall of the high pressure gas cylinder.

Also, according to the above-described exemplary embodiments of the present invention, it is possible to prevent a defect on a plating layer formed on a threaded portion of the high pressure gas cylinder by preventing an occurrence of an air pocket since plating is performed by forcefully circulating a plating solution.

Also, according to the above-described exemplary embodiments of the present invention, it is possible to provide a plated surface of a threaded portion without micro-sized foreign substances since the micro-sized foreign substances are forcefully discharged to an outside to prevent foreign substances from existing on pits of a threading portion.

Also, according to the above-described exemplary embodiments of the present invention, it is possible to appropriately control thickness distribution of a plating layer being formed on ridges and pits of the threaded portion by controlling a diameter of an anode pipe.

Also, according to the above-described exemplary embodiments of the present invention, it is possible to control thickness of a plating layer according to locations of a threaded portion by partially isolating an outer surface of an anode pipe and by preventing electric charges between a threaded portion and the anode pipe from smoothly circulating.

Although a few exemplary embodiments of the present invention have been shown and described, the present invention is not limited to the described exemplary embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents. 

1. A method for plating a threaded portion of a high pressure gas cylinder, the method comprising: providing a high pressure gas cylinder having a gas containing portion and a threaded portion being formed on a top of the gas containing portion; locating an anode pipe, in which a plating solution passage is formed, inside the threaded portion; forming a closed chamber containing the threaded portion and the anode pipe; forming a flux of the plating solution inside the closed chamber; and forming a voltage difference between the anode pipe and the threaded portion, and plating the threaded portion.
 2. The method of claim 1, wherein, in the forming of the closed chamber, a bottom sealing portion isolates a bottom of the threaded portion from the gas containing portion, and a top sealing portion, which is formed in correspondence to the bottom sealing portion, isolates a top of the threaded portion from an outside to form the closed chamber.
 3. The method of claim 1, wherein, in the forming of the flux of the plating solution, the plating solution flows from the plating solution passage into the closed chamber so as to form the flux of the plating solution around the anode pipe.
 4. The method of claim 1, wherein, in the forming of the flux of the plating solution, the plating solution flows from the closed chamber into the plating solution passage so as to form the flux of the plating solution around the anode pipe.
 5. The method of claim 2, wherein the bottom sealing portion comprises a supporter and a rubber piece on a bottom of the anode pipe, the supporter has a diameter less than an inside diameter of the threaded portion, and the rubber piece is located on a top of the supporter and has a diameter greater than the inside diameter of the threaded portion.
 6. The method of claim 2, wherein the bottom sealing portion comprises a balloon portion, which is formed on the bottom of the anode pipe, and an inner pipe is formed inside the anode pipe so as to insert a fluid into the balloon portion.
 7. The method of claim 1, wherein, in the plating of the threaded portion, a plating layer is formed with thickness of approximately 1 to 100 μm.
 8. The method of claim 1, wherein, in the plating of the threaded portion, a nickel chloride solution is utilized to embody the plating layer, from the nickel chloride solution, the nickel chloride solution having a nickel chloride concentration of approximately 50 to 500 g/L, a boric acid concentration of approximately 5 to 50 g/L, a pH in the range of approximately 0.5 to 6.5, a use temperature of approximately 20 to 95° C., and a use voltage of approximately 3 to 20 V.
 9. The method of claim 1, wherein, in the plating of the threaded portion, a nickel sulfate solution is utilized to embody the plating layer, from the plating solution, the nickel sulfate solution having a nickel sulfate concentration of 100 to 500 g/L, a boric acid concentration of approximately 5 to 50 g/L, a nickel chloride concentration of approximately 2 to 80 g/L, a pH in the range of approximately 1 to 6.5, a use temperature of approximately 20 to 95° C., and a use voltage of approximately 3 to 20 V.
 10. The method of claim 1, wherein, in the plating of the threaded portion, a nickel sulfamate solution is utilized to embody the plating layer, from the plating solution, the nickel sulfamate solution having a nickel sulfamate concentration of 100 to 500 g/L, a boric acid concentration of approximately 5 to 50 g/L, a nickel chloride concentration of approximately 2 to 80 g/L, a pH in the range of approximately 1 to 6.5, a use temperature of approximately 20 to 95° C., and a use voltage of approximately 3 to 20V.
 11. The method of claim 1, wherein, in the plating of the threaded portion, a nickel fluoborate solution is utilized to embody the plating layer, from the plating solutions, the nickel fluoborate solution having a nickel fluoborate concentration of 40 to 500 μL, a boric acid concentration of approximately 5 to 50 g/L, a pH in the range of approximately 1 to 6.5, a use temperature of approximately 20 to 95° C., and a use voltage of approximately 3 to 20 V.
 12. The method of claim 1, wherein a diameter of the anode pipe is controlled so as to control the thickness of the plating layer, the plating layer being formed on ridges and pits of the threaded portion.
 13. The method of claim 1, wherein a surface of the anode pipe is partially masked so as to control the thickness of the plating layer according to each location of the threaded portion.
 14. The method of claim 1, wherein the providing of the high pressure gas cylinder provides the high pressure gas cylinder in which the plating layer is formed on an inside wall thereof.
 15. An apparatus for plating a threaded portion of a high pressure gas cylinder which has a gas containing portion and a threaded portion being formed on a top of the gas containing portion, the apparatus comprising: an anode pipe, on which a plating solution passage is formed; a bottom sealing portion being formed on a bottom of the anode pipe, and isolating a bottom of the threaded portion from the gas containing portion; a top sealing portion being formed in correspondence to the bottom sealing portion, and isolating a top of the threaded portion from an outside; and a plating solution supplier supplying a plating solution to the anode pipe and the closed chamber.
 16. The apparatus of claim 15, wherein the plating solution passage is formed on a location which corresponds to the bottom of the threaded portion, and an inlet/outlet for the plating solution is formed on a side of the top sealing portion.
 17. The apparatus of claim 16, wherein the plating solution flows into the closed chamber through the plating solution passage, the flowed plating solution is discharged to the outside through the inlet/outlet for the plating solution so that a flux of the plating solution is formed around the anode pipe.
 18. The apparatus of claim 16, wherein the plating solution flows from the closed chamber into the plating solution passage, and the flowed plating solution is discharged to the outside through an opened hole of the anode pipe so that flux of the plating solution is formed around the anode pipe.
 19. The apparatus of claim 15, wherein the bottom sealing portion comprises a supporter and a rubber piece on a bottom of the anode pipe, the supporter has a diameter less than an inside diameter of the threaded portion, and the rubber piece is located on an upper portion of the supporter and has a diameter greater than the inside diameter of the threaded portion.
 20. The apparatus of claim 15, wherein the bottom sealing portion comprises a balloon portion being formed on the bottom of the anode pipe, and an inner pipe is formed inside the anode pipe so as to insert a fluid into the balloon portion.
 21. The apparatus of claim 15, wherein a diameter of the anode pipe is controlled to control the thickness of the plating layer which is formed on ridges and pits of the threaded portion.
 22. The apparatus of claim 15, wherein a surface of the anode pipe is partially masked so as to control the thickness of the plating layer at each location of the threaded portion. 